Performance improvement of Cu2ZnSn(S,Se)4 solar cells by introducing the tiny rare-earth Ce3+

Through introducing the extra tiny Ce 3+ in the precursor solution, the incorporated Ce is found to be located at the grain boundaries of Cu 2 ZnSn(S,Se) 4 absorber in form of Na-Ce-Se phase, limit their Sn-related defects, and increase Cu 2 ZnSn(S,Se) 4 device efficiencies from 6.77 % ( R Ce = 0) to 9.14 % ( R Ce = 0.024) with a decreased V OC,Def of 644 mV. • Tiny rare-earth Ce 3+ doping can form the Na-Ce-Se phase and reduce the harmful Sn-related deep energy level defects of Cu 2 ZnSn(S,Se) 4 thin films. • A decreased open-circuit voltage deficits for tiny Ce-doped Cu 2 ZnSn(S,Se) 4 device can be obtained. • The efficiency of Cu 2 ZnSn(S,Se) 4 devices can be improved from 6.77 % ( R Ce = 0) to 9.14 % ( R Ce = 0.024). Controlling the formation of harmful defects plays an important role in obtaining high efficiency Cu 2 ZnSn(S,Se) 4 (CZTSSe) solar cells. Here, the extra tiny Ce 3+ is used to reduce the cation disordering of absorber, improving the performance of devices. Based on the ionic liquid-based solution approach, we prepared the different Ce-doped CZTSSe devices and studied the mechanism of trace Ce-doping. By means of XRD, SIMS, and EDS measurements, the incorporated Ce is found to be located at the grain boundaries in form of Na-Ce-Se phase. Further combined with the results of Raman, c-AFM, I - V , and EQE measurements, the trace Ce-doping is thought to limit the Sn-related defects of absorber and enhance the performance of devices from 6.77 % ( R Ce = 0) to 9.14 % ( R Ce = 0.024). Our conclusions will provide the new insights for further increasing CZTSSe-based solar cell efficiency by defect engineering.